"This tree removes ancient-386-CPUs support and thus zaps quite a bit of complexity [...] which complexity has plagued us with extra work whenever we wanted to change SMP primitives, for years. Unfortunately there's a nostalgic cost: your old original 386 DX33 system from early 1991 won't be able to boot modern Linux kernels anymore. Sniff. I'm not sentimental. Good riddance." Almost 21 years of support for a professor. Not bad.

I still have my 386SX-25 with the 80387 with 32Mb RAM. Although "back in the day" it only had 5Mb (4x1024kb + 4x256kb). This makes me sad, being an avid retro-computing enthusiest, stripping back, compiling and fiddling on the old girl and several other machines has been one of the pointless pleasures in my life

I bought this specific machine's mobo + processor in really early 1992 when I first read about Linux because my NECV20 wasn't going to cut it past Xenix 8086.

It's theoretically possible. Back then some computers used "expanded memory", where you might have a pool of RAM (e.g. 256 blocks of 64 KiB) that the CPU can't access and a small number of those block/s could be switched into the CPU's address space (e.g. so that the CPU could access any 2 of the 64 KiB blocks at a time).

For example; you could have "almost 16 MiB" of normal RAM that uses "almost 16 MiB" of the CPU's address space; plus another 16 MiB of "expanded RAM" that only uses 128 KiB of the CPU's address space.